The present invention relates to a double-walled stackable and de-stackable paperboard cup comprising an inner cup, an outer sleeve with a gap between inner cup and outer sleeve, said outer sleeve being attached below the drinking lip of the inner cup, also comprising a rolled lip applied to the lower end of the outer sleeve and disposed on the inner sleeve.
A container of this type is prior art in European patent 1 227 042. A heat-insulating cup is described, which is formed by two conical sleeves, whereby the inner sleeve comprises an inwardly directed groove, which serves to permit the stacking of an identical cup inside said cup already stacked. The inwardly directed groove, formed by means of rolling, should serve to provide the cup with good stacking and de-stacking properties so that a number of stacked cups do not get stuck inside one another. Experience has shown that the stacking properties are satisfactory for approximately 20 cups. If more than this number of cups are stacked together, they become stuck. This is caused in particular by axial pressure, directed from the cup opening to the cup bottom, which is generated by the weight of many cups stacked on top of each other. Even the moderate setting down of 50 packed and stacked cups can result in them becoming stuck to one another. The cause of the cups becoming stuck together must be seen in the insufficient stiffness of the groove, which, however, cannot be improved while applying this method of production, as the rolling process results in a weakness in the material.
In European published patent 1 227 043, a better thermal insulation of the cup disclosed is utilized, which cup possesses the same stacking properties of the above described cup.
One-walled stackable paperboard cups are disclosed in Japanese published patent application 2000-302132, which achieve a stacking of the inner paperboard cup in the outer paperboard cup in the upper area of the cup by means of clamping. This clamping results in the paperboard cups not being easily de-stackable. In addition, the one-walled design leads to a low thermal insulation.
It is an object of the present invention to significantly improve the stacking and de-stacking properties of paperboard cups of the above mentioned type. In particular, in contrast to prior art, a significantly greater number of cups should be stackable, which in particular do not become stuck to one another when a large number of stacked cups are set down with a jolt, or when in any other way a high level of axial pressure acts on the stacked cups, for example when a cup magazine is filled.
This object has been achieved in accordance with the present invention in that on the outer sleeve, a shoulder-shaped stacking stopper is designed, which is assigned to the drinking lip.
In non-generic one-walled plastic cups it is known (Japanese published patent 33 83 698) that the sleeve is provided with a stacking stopper, which is supported on the upper inner rim during stacking. The stacking stopper is in this case designed in such a way that in the case of too high pressure, in particular in the case of a downward jolt, the stacked cups may become stuck inside one another, because the distribution of the forces in the area of the stacking stopper at too high an axial pressure can result in the cup wall of the stacked cup giving way inwardly.
In the case of the cup according to the present invention, the stacking shoulder is applied to the outer sleeve, that is, the stacking shoulder is not located on that sleeve on which the drinking lip is located. This gives rise to two advantages which no stackable cup has yet possessed. Firstly, the stacking stopper can be applied in such a way that the stacked cup is supported there where the stacking cup possesses good stability, namely at the drinking lip. Secondly, by means of the geometric shape of the stacking stopper, the acting force of the stacked paperboard cup on the drinking lip of the stacking paperboard cup is directed normally onto the surface of the drinking lip. Thus a giving way of the outer sleeve of the stacked paperboard cup is avoided, even at very high axial pressure which could act on the cup opening, whereby a very stable design is achieved.
The paperboard cup can be made in a variety of embodiments. The inner cups of paperboard cups having a low volume do not need to comprise an inner shoulder, as the drinking lip for smaller cup openings is sufficiently stable in radial direction. In the case of larger paperboard cups, the application of an inner shoulder to support the stacking stopper is recommended. The application of an inner shoulder increases the radial stability of the stacking stopper. In addition the surface temperature of the outer sleeve can be altered by the application of the shoulder. The inner shoulder increases the gap between the inner cup and the outer sleeve, whereby the insulating effect of the double-walled design is is further increased. Also, there is a relatively wide choice of supporting positions of the rolled lip.
In order to achieve an economical, material-saving manufacture of the paperboard cup, the support of the rolled lip can be located several millimeters above the bottom of the cup without the stacking properties being altered hereby. If maximum stability of the paperboard cup is required, then the support of the rolled lip should be located exactly at the level of the cup bottom. In this embodiment, the paperboard cup is visually at its most attractive, resulting in the highest possible sales.
The present invention also relates to a process in which the paperboard cup is manufactured. An outer sleeve, comprising a rolled lip, is hereby made during preliminary procedural steps, which are not described here. The stacking stopper is subsequently applied. This takes place in a forming station, which comprises the following components: a lower cup support, a cup take-up and the pressing arrangement. After the stacking stopper has been applied, the outer sleeve is transported to further stations, where it is equipped with the inner cup and finished.